Subject: RE: [VRRP] Reviving draft-ietf-vrrp-ipv4-timers-02

From: "Fioramonti, Joseph" <[email-masked]>
Date: Wed, 4 Apr 2007 09:23:57 -0400

> 
> > The reason to add units is not that we need it today (we don't).  Its
> > because someone might need it in the future.
> 
> If someone needs smaller units or larger units or different units
> in the future, we have a plan: they should use a different packet
> type for exactly the same reasons we are using a different packet
> type.
> 
> If, on the other hand, no one ever needs different units in the
> future, then we'd be wasting effort implementing them now.
> 
> > RFC 2338/3768 and draft-ietf-vrrp-ipv6-spec-08 both say that
> > the purpose for
> > sending the advertisement interval is to troubleshoot
> > misconfigured routers.
> > I assume that would still be at least a part of the purpose.
> > Do you have
> > some other purpose in mind?
> 
> The exist protocol versions mistakenly think the advertisement
> interval needs to be synchronized, but that's only because the
> advertisement interval and the timeout interval are synonymous
> for the current protocol's purposes: in essence we were always
> checking the timeout interval, but we were doing it by
> comparing the value divided by 3. As you yourself pointed out,
> the correlation no longer holds because both intervals need
> to be independently configurable. When we revisit the
> assumptions of the existing protocols now that we realize the
> two variables are independent, it's plain that only the timeout
> interval needs to be synchronized for correct protocol behavior.
> 
> Two cooperating routers having different advert intervals is
> no longer a misconfiguration. It's just an implementation
> decision, not a problem that needs troubleshooting.

Given that, then do we even need to send the timeout interval?
Would it be valid to have different timeout periods configured?

--Joe.

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From: "Don Provan" <[email-masked]>
Date: Wed, 4 Apr 2007 13:23:54 -0700

> Would it be valid to have different timeout periods configured?

I do not think it would be valid, no. I think there are several
ways that mismatched timeouts could lead to problems, exactly
the same problems that led to the existing specification
requiring confirming the Advertisement Interval.

By the way, I've been talking as if there's an existing concept
of "timeout interval", but actually it would be an addition.
Master_Down_Interval would be Timeout_Interval + Skew_Time.
And while Advertisement_Interval would be configurable, as we've
agreed, it would be limited to being no greater than
Timeout_Interval / 3.

-don